1. Field of the Invention
The present invention relates to material suitable for the interior or exterior trim of an automobile (hereinafter simply called an “interior or exterior trim material”) which comprises a thermoplastic elastomer having improved weather resistance due to incorporation of a specific UV absorber; i.e., alkyl benzoate having a specified chemical structure. More particularly, the present invention relates to an interior or exterior trim material having improved weather resistance and resistance to weather-induced coloring.
2. Background Art
Conventionally, vinyl chloride resins have been widely used as interior or exterior trim materials. However, use of vinyl chloride resins has recently been restricted because of concerns in relation to environmental pollution, calling for substitution by non-halogen resins.
One possible substitute may be realized by use of a thermoplastic elastomer having resin properties suitable for an interior or exterior trim material. An interior or exterior trim material is required to have high weather resistance and resistance to weather-induced coloring, because the material is exposed to strong sunshine at high temperature while, for example, the automobile is parked outdoors.
Conventionally, a variety of UV absorbers and photostabilizers have been disclosed, and use method of these compounds has been suggested for imparting weather resistance to polyolefin resins used as polymer materials for general molding. Examples of UV absorbers include benzotriazole UV absorbers, benzophenone UV absorbers, phenoltriazine UV absorbers, and alkyl or aryl benzoate UV absorbers; and examples of photostabilizers include hindered amine photostabilizers.
For example, Japanese Patent Application Laid-Open (kokai) No. 54-21450 discloses a method for improving weather resistance of polyolefin resins by combined use of 3,5-di-tert-butyl-4-hydroxybenzoic acid hexadecyl ester (which is an alkyl benzoate UV absorber), and a benzotriazole UV absorber or a benzophenone UV absorber. Japanese Patent Application Laid-Open (kokai) No. 55-54339 discloses a method for improving weather resistance of polypropylene resins by combined use of the above-mentioned 3,5-di-tert-butyl-4-hydroxybenzoic acid hexadecyl ester and pentaerythritol dialkyldiphosphite. Japanese Patent Application Laid-Open (kokai) No. 56-62835 discloses a method for improving weather resistance of polyolefin by combined use of the above-mentioned 3,5-di-tert-butyl-4-hydroxybenzoic acid hexadecyl ester and a hindered amine photostabilizer.
Regarding the above-mentioned 3,5-di-tert-butyl-4-hydroxybenzoic acid hexadecyl ester, which is an alkyl benzoate UV absorber, Japanese Patent Application Laid-Open (kokai) No. 58-84839 discloses use thereof for pipes made of poly-1-butene; Japanese Patent Application Laid-Open (kokai) No. 1-62360 discloses use of the same for polypropylene resins which are subjected to radiation sterilization and used in the field of medicine, and Japanese Patent Application Laid-Open (kokai) No. 7-188473 discloses use of the same as materials in the agricultural field.
Japanese Patent Application Laid-Open (kokai) No. 7-179719 discloses use of 3,5-di-tert-butyl-4-hydroxybenzoic acid 2,4-di-tert-butylphenyl ester (which is an aryl benzoate UV absorber) as an automobile material.
Thus, a variety of methods have been disclosed for improving weather resistance of polymer materials for general molding. However, no known UV absorbers or photostabilizers provide satisfactory effects. Thermoplastic elastomers which are to be used as substitutes for interior or exterior trim materials are no exception; they also involve the same problems. However, no method for improving properties of thermoplastic elastomers has been known. An object of the present invention is to solve the above problems inherent to thermoplastic elastomers.